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    <title>Document</title>
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<script>
  var reg =
    /^[1-9]$/ ||
    /^[1-9]$\d/ ||
    /^1[0-9][0-9]$/ ||
    /^1[0-4][0-9]$/ ||
    /^25[0-5]$/;
  var str = prompt("请输入要检测的数值，注意范围为0-255");
  console.log(reg.test(str));
</script>
